Synthesis And Properties Of Conducting Polymer-ZnO Nanocomposite Electrochromic Materials

Electrochromic materials as a new type of intelligent materials have wide potential applications in electronics,energy,construction and military.Conducting polymers have been considered one of the main research on electrochromic materials due to various structures,easy modification,rich colors,high optical contrast and fast response speed.In recent years,conducting polymer-inorganic nanocomposite has drawn more attention since they can combine the advantages of both components and may offer special properties through the reinforcement or modification of each other.In this paper,conducting polymer-ZnO nanocomposites were fabricated to improve the electrochromic properties.The effect and the surface modification of different ZnO nanostructures(such as nanoridges,nanorods,nanosheets)on the electrochromic properties were explored in detail.For the first part,poly(1,4-bis(2-thienyl)-benzene)(PBTB)-ZnO nanoridges composite was synthesized via solvothermal method and electrochemical polymerization.SEM,XRD,cyclic voltammetry and FT-IR spectra confirm that PBTB-ZnO nanocomposite film is successfully obtained.The composite film exhibits good electrochemical activity and electrochromism with reversible color changes.The PBTB film shows optical contrast of 22%at 610 nm,29%at 1100 nm,switching time of 2 s at 1100 nm and can retain 50%of its original electroactivity after 300 cycles.However,the nanocomposite film presents higher optical contrast of 26%at 609 nm,39%at 1100 nm,shorter switching time of 0.9 s at 1100 nm and it can retain up 90%of its original electroactivity after 300 cycles.Therefore,the results demonstrate that the electrochromic performances are significantly enhanced through incorporating PBTB with ZnO nanoridges.Moreover,the possible mechanism for the enhanced properties is proposed that reveals the diffusion process of the ions in nanocomposite film.The introduction of ZnO nanoridges can increase the contact area,shorten the diffusion distance and facile the ion doping-dedoping,resulting in more excellent electrochromic properties.In addition,the electrochemical impedance illustrates the composite film has a lower charge transfer resistance leading to the faster diffusion speed,which further provides the experimental and theoretical basis for the above theory.In this second part,poly(4,4',4"-tris[4-(2-bithienyl)pheny]a mine)(PTBTPA)-ZnO nanorods composite was synthesized via solvothermal method and electrochemical polymerization.SEM,XRD,CV and FT-IR spectra confirm that PTBTPA-ZnO nanocomposite film is successfully obtained.The composite film exhibits good electrochemical activity and electrochromism with reversible color changes.The PTBTPA film shows optical contrast of 34%at 460 nm,42%at 710 nm and 52%at 1100 nm,switching time of 1.63 s at 1100 nm and can retain 75%of its original electroactivity after 500 cycles.While the nanocomposite film shows higher optical contrast of 37%at 460 nm,42%at 710 nm and 65%at 1100 nm,shorter switching time of 0.92 s at 1100 nm and can retain 97%of its original electroactivity after 500 cycles.Therefore,the results demonstrates that the electrochromic performances are significantly enhanced through incorporating PTBTPA with ZnO nanorods.Moreover,the possible mechanism for the enhanced properties is proposed that reveals the diffusion process of the ions in nanocomposite film.The introduction of ZnO nanorods can increase the contact area,shorten the diffusion distance and facile the ion doping-dedoping,resulting in more excellent electrochromic properties.In this third part,PTBTPA-ZnO nanosheets core-shell composite was synthesized via electrodeposition combining with electropolymerization method.SEM,TEM,CV and FT-IR spectra confirm that PTBTPA-ZnO core-shell composite film is successfully obtained.The composite film exhibits good electrochemical activity and electrochromism with reversible color changes.The PTBTPA film shows optical contrast of 51.8%,switching time of 1.95 s at 1100 nm and loses almost most of its electroactivity after 1000 cycles.While the nanocomposite film shows higher optical contrast of 68.7%at 1100 nm,faster switching time of 0.96 s at 1100 nm and can retain 70%of its original electroactivity after 1000 cycles.The core-shell composite structure is believed to be responsible for the enhanced electrochromic performance.On one hand,the porous structure with loose inner space can facilitate counterions into the polymer film and shorten the diffusion distance,devoting to the higher optical contrast and faster switching speed;on the other hand,the larger contact area can enhance the adhesion between the polymer and the ITO electrode,contributing to better electrochemical cyclic stability.Interface issue has been one of the bottlenecks for the improvement on the properties of nanocomposite materials.The last part initially explored the interface issues and solutions existing in organic-inorganic nanocomposite materials.Different silane coupling agents(3-mercaptopropyltriethoxysilane(MTES),3-a minopropyltriethoxysilane(ATES),phenyltriethoxysilane(PTES))were used to modify the surface of ZnO nanorods.The effect of surface modification on the electrochromic properties of PTBTPA-ZnO nanocomposite film were investigated.Compared with the untreated composite film,the composite films after treatment by MTES and ATES show little change of the optical contrast but slower response speed and bad electrochemical stability.However,the composite film after treatment by PTES shows optical contrast of 32%at 430 nm,49%at 700 nm and 68%at 1100 nm,switching time(colored time and bleached time)of 1.49 s and 2.81 s(1100 nm),1.33 s and 2.77 s(700 nm),1.19 s and 2.68 s(430 nm)and can retain 96%and 86.6%of its original electroactivity after 500 and 1000 cycles.Therefore,the composite film after treatment by PTES shows the enhanced electrochromic performance,especially the electrochemical stability.Currently,the research on the surface treatment in enhancing the electrochromic performance has been rarely reported,this work provides some theoretical significance and reference for conducting polymer-inorganic nanocomposite electrochromic system.